Automotive fuel systems require a fuel tank, a filler pipe and cap therefor for filling the tank with fuel, a fuel pump and associated fuel lines, and a fuel level sensor. The fuel tank has a rigid tank sidewall usually composed of a metallic or plastic material, wherein the tank sidewall contains the fuel. The filler pipe extends from an opening in the fuel tank to an external opening of the body of the vehicle. The filler cap is removably affixed to the filler pipe, so as to be removed by a driver when fueling the motor vehicle and reaffixed, such as by threading, when fueling is completed. The fuel pump is electrically operated, and is generally designed to deliver a predetermined flow rate of fuel to the engine via a delivery fuel line, and excess fuel is returned to the fuel tank via a return fuel line. Fuel level sensing may be accomplished by any modality known, including float based systems.
Fuel vapor emissions have become increasingly noted a concern which motor vehicle manufacturers must address. One source of fuel vapor emissions concerns tank ventilation, which must be provided so that fuel may be extracted from the fuel tank by the fuel pump, as the volume of fuel taken out by the pump is replaced by atmospheric pressure air. Unfortunately, this same ventilation provision allows escape of fuel vapors. Another fuel vapor emissions problem concerns refueling, whereduring fuel displaces fuel vapor from the tank. To overcome this vapor emissions source, a fuel vapor control system (FVCS) must be included with the fuel system of the vehicle. A typical FVCS includes vapor lines, a carbon canister, a purge solenoid, a vent solenoid, an onboard refueling vapor recovery system, and an onboard diagnostics II (OBD II) pressure sensor.
It would be extremely beneficial if somehow a fuel system could be devised which has fuel vapor emission levels that are very low.